Experiences with FMW ceramic underfloor heating system?

Hello dear forum participants,

the FMW ceramic underfloor heating system has been on the market for 30 years, but unfortunately it apparently has not gained acceptance and seems to have stagnated there.... or? So far I have not found anyone who has ever heard of the FMW ceramic underfloor heating system, let alone installed it or had it installed...

The principle of this underfloor heating system sounds very, very interesting, but I see an obvious contradiction in the description: "It does not heat the entire screed as usual and due to the bricks used, this floor retains the heat longer than conventional screed."

Furthermore, the construction with dry fill without impact sound insulation, as described, seems very daring to me. Perlite etc. do not have good values regarding impact sound insulation...

Then a wood fiberboard as a base for the dry fill, as also described there, is quite unusual, isn’t it?

Unfortunately, there are many examples that the best products do not necessarily prevail in the market, and many good developments have come from Franconia.... Could it possibly be due to the price, the effort for installation, or does the company simply have no decent sales force?

Many, many thanks for your experience reports or the contact referrals to people who have successfully installed this system or have had it installed...

Best regards

Maddin

I think it has not caught on because of the rather elaborate installation. After all, the effort to create a flat and load-bearing surface is considerably higher.

The ceramic is very good for heat storage – that is beyond question.

How does the insulation look here? It should be present under the tiles so that you don't end up warming the cellar ceiling, etc.
I wouldn’t do that with loose fill either, since the tiles are relatively small and therefore don’t create a really solid, load-bearing composite.
The connecting pieces don’t look stable enough to withstand high shear forces, especially since the material is very brittle.

Hello Joerg24,

thank you for your hints. Here is the information from the manufacturer: The FMW system stones actually form a load-bearing, ready-to-cover subfloor in combination with the grout. This has often been doubted, also by architects, but it works without a doubt, among other things because the panels as well as the gaps between the stones are filled and thus glued together with the grout. After grouting, the individual panels no longer move, only the complete floor as a composite does. Since the FMW system is normally operated as a low-energy system with temperatures not exceeding 30 °C, the thermally caused expansions are no higher than on warm summer days. (The system of course can also be operated at higher temperatures without any problems). The FMW system has already been installed on insulation made of mineral wool or horsehair. The only problem here arises during the phase of installing the panels or during the pouring process due to pressing down. After grouting, the system forms a load-bearing panel which compresses the insulation evenly over the entire surface up to a certain level. In general, we have not had a single floor break in any form in 30 years. You also do not need expansion joints in the upper covering on large surfaces. This is due to the special laying pattern (herringbone pattern) of the FMW stones. No stress peaks can arise here that would lead to cracks in the subfloor—and thus in the upper floor—because the longest continuous joints are 45 cm long. Floors of 300 and 550 sqm have already been installed on one surface without expansion joints.

This is how our floor constructions are supposed to look now, and I thank you for critical consideration...

Living room (heated below, ancillary rooms):

approx. 31m², max. 7 cm available above raw floor:

- 14 mm tile covering in thin bed
- 35 mm FMW ceramic floor heating system with 15x1mm copper pipe
- 1 mm DELTA-REFLEX foil (aluminum coating upwards)
- 5 mm impact sound insulation (XPS heavy foam 35kg/m³, 0.232 m²K/W)
- 20 mm ISOPERL-/cement mixture to level the very uneven raw floor
- 12 cm reinforced concrete ceiling (provided on site)

Conservatory (5° - 30°, depending on outside temperature and solar radiation, heated below, bathroom, bedroom, office):

approx. 28m², max. 17 cm available above raw floor...

- 14 mm tile covering in thin bed
- 35 mm FMW ceramic floor heating system with 15x1mm copper pipe
- 1 mm DELTA-REFLEX foil (aluminum coating upwards)
- 100 mm polystyrene, PS 20 or PS 30 SE
- 1 mm DELTA-REFLEX foil (aluminum coating downwards)
- 20 mm impact sound insulation
- 18 cm reinforced concrete ceiling (provided on site)

Are the floor constructions okay as described?

I am very grateful for suggestions and possible improvements!!!